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Giant's Causeway,headland on the north coast of Moyle dist., N Northern Ireland, NE of Coleraine; est. as a national trust territory in 1961. Extending 3 mi (4.8 km) along the coast, it consists of thousands of basaltic columns of volcanic origin, forming three natural platforms (Little, Middle, and Grand Causeway). Several large caves and rock formations exist. According to legend, the Causeway was built for giants to travel across to Scotland. A ship of the Spanish Armada was wrecked in Port-na-Spania (Spanish Bay) nearby.
a surface of basaltic (less frequently, andesitic) lava exposed after the ablation of the upper vesicular layer and broken by vertical partings into prisms with five or six faces. The convex tops of the prisms resemble a roadway paved with giant blocks (0.5–1.5 m across).